[summary of the invention]
Goal of the invention of the present invention is for overcoming above-mentioned defective of the prior art, a kind of preparation method of cell positive material of LiFePO4 is provided, to reach processing characteristics and the tap density of improving cell positive material, improve the purpose of the volume and capacity ratio of positive electrode.
To achieve the above object of the invention, the cell positive material preparation method of LiFePO4 provided by the invention comprises following steps:
S1. in Li: the mol ratio ratio of Fe: P=1~1.05: 1~1.05: 1~1.05 takes by weighing lithium source, ferrous salt, phosphate, mixes to be placed on and carries out ball-milling treatment in the ball grinder;
S2. the mixture behind the ball milling is sent in the sintering furnace and under 300-350 ℃ of temperature, carried out the roasting preliminary treatment;
S3. pretreated mixture once more behind the ball milling, is sent into the sintering kiln roasting 24~48h of nitrogen and/or inert gas shielding;
S4. the ball milling screening is taken out in furnace temperature cooling back; with screening products obtained therefrom and lithium salts positive electrode except that LiFePO4 press mass ratio 90: 10~95: 5 mixed ball milling; and then send in the sintering furnace of nitrogen and/or inert gas shielding and carry out the after baking granulation; ball milling is taken out in furnace temperature cooling back, promptly gets the cell positive material of LiFePO4.
Preferably, among the above-mentioned steps S1, described lithium source is to be selected from least a in lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, the lithium oxalate, ferrous salt is to be selected from least a in ferrous oxalate, ferrous acetate, the ferrous sulfate, and phosphate is to be selected from least a in ammonium phosphate, diammonium hydrogen phosphate, the ammonium dihydrogen phosphate.
Preferably, among the above-mentioned steps S1, the process conditions of described ball-milling treatment are that ethanol or propyl alcohol are decentralized medium, 400~600 rev/mins of ball milling speed, ball milling duration 4~6 hours.
Preferably, among the above-mentioned steps S2, the pretreated time of described roasting is 4~6 hours.
Preferably, among the above-mentioned steps S3, described sintering temperature is 600~800 ℃.
Preferably, among the above-mentioned steps S4, described lithium salts positive electrode except that LiFePO4 is cobalt acid lithium, LiMn2O4, lithium nickelate or nickle cobalt lithium manganate.
Preferably, among the above-mentioned steps S4, the process conditions of described after baking are 250~600 ℃ of temperature, roasting time 12~48 hours.
As can be seen from the above technical solutions, the preparation method of the cell positive material of LiFePO4 provided by the present invention, adopted secondary granulation technology to improve the conventional less shortcoming of lithium iron phosphate positive material particle diameter, both can obtain the lithium iron phosphate positive material of better high rate performance, can also improve the processing characteristics and the tap density of positive electrode effectively, improve the volume and capacity ratio of material.
[embodiment]
Embodiment 1
With Li: Fe: P=1: 1.05: 1 mol ratio ratio takes by weighing LiOHH
2O, FeC
2O
4And NH
4H
2PO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 350 ℃, handle 6h.Pretreated mixture is carried out sending into behind the ball milling again in the sintering furnace of nitrogen protection with 700 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and nickle cobalt lithium manganate positive electrode according to 95: 5 mixed ball millings of mass ratio after; send into once more in the sintering furnace of nitrogen protection and carry out secondary granulation, temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 2
With Li: Fe: P=1: 1: 1 mol ratio ratio takes by weighing Li
2CO
3, FeC
2O
4And NH
4H
2PO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 350 ℃, handle 6h.Pretreated mixture is carried out sending into behind the ball milling again in the sintering furnace of nitrogen protection with 700 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and lithium cobaltate cathode material according to 90: 10 mixed ball millings of mass ratio after; send into once more in the sintering furnace of nitrogen protection and carry out secondary granulation, temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 3
With Li: Fe: P=1: 1: 1 mol ratio ratio takes by weighing LiNO
3, Fe (C
2H
3O
2)
24H
2O and (NH
4)
2HPO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 350 ℃, handle 6h.Pretreated mixture is carried out sending into behind the ball milling again in the sintering furnace of nitrogen protection with 700 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and manganate cathode material for lithium according to 92: 8 mixed ball millings of mass ratio after; send into once more in the sintering furnace of nitrogen protection and carry out secondary granulation, temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 4
With Li: Fe: P=1: 1.05: 1.05 mol ratio ratio takes by weighing Li
2C
2O
4, Fe (C
2H
3O
2)
24H
2O and (NH
4)
2HPO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 330 ℃, handle 4h.Pretreated mixture is carried out sending into behind the ball milling again in the sintering furnace of helium protection with 800 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and lithium cobaltate cathode material according to 95: 5 mixed ball millings of mass ratio after; send into once more in the sintering furnace of helium protection and carry out secondary granulation, temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 5
With Li: Fe: P=1.05: 1: 1.05 mol ratio ratio takes by weighing LiC
2H
3O
2, FeSO
4(NH
4)
3PO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 300 ℃, handle 5h.Pretreated mixture is carried out sending into behind the ball milling again in the mixed gas protected sintering furnace of nitrogen and helium with 600 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and manganate cathode material for lithium according to 95: 5 mixed ball millings of mass ratio after; send into once more in the mixed gas protected sintering furnace of nitrogen and helium and carry out secondary granulation; temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 6
With Li: Fe: P=1.05: 1.05: 1 mol ratio ratio takes by weighing LiOHH
2O, FeSO
4(NH
4)
3PO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 330 ℃, handle 4h.Pretreated mixture is carried out sending into behind the ball milling again in the sintering furnace of helium protection with 800 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and nickle cobalt lithium manganate positive electrode according to 90: 10 mixed ball millings of mass ratio after; send into once more in the sintering furnace of helium protection and carry out secondary granulation, temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 7
With Li: Fe: P=1.05: 1: 1 mol ratio ratio takes by weighing LiC
2H
3O
2, FeC
2O
4And NH
4H
2PO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 300 ℃, handle 5h.Pretreated mixture is carried out sending into behind the ball milling again in the mixed gas protected sintering furnace of nitrogen and helium with 600 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and manganate cathode material for lithium according to 90: 10 mixed ball millings of mass ratio after; send into once more in the mixed gas protected sintering furnace of nitrogen and helium and carry out secondary granulation; temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 8
With Li: Fe: P=1: 1: 1.05 mol ratio ratio takes by weighing Li
2CO
3, FeSO
4(NH
4)
2HPO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 4h, after finishing mixture sent in the box type furnace and with about 330 ℃, handle 6h.Pretreated mixture is carried out sending into behind the ball milling again in the sintering furnace of nitrogen protection with 800 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and nickle cobalt lithium manganate positive electrode according to 92: 8 mixed ball millings of mass ratio after; send into once more in the sintering furnace of nitrogen protection and carry out secondary granulation, temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Embodiment 9
With Li: Fe: P=1: 1.05: 1 mol ratio ratio takes by weighing Li
2C
2O
4, Fe (C
2H
3O
2)
2(NH
4)
3PO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 300 ℃, handle 5h.Pretreated mixture is carried out sending into behind the ball milling again in the sintering furnace of nitrogen protection with 600 ℃ of roasting 24h; Take out the ball milling screening with the furnace temperature cooling; to sieve products obtained therefrom and lithium cobaltate cathode material according to 92: 8 mixed ball millings of mass ratio after; send into once more in the sintering furnace of nitrogen protection and carry out secondary granulation, temperature is controlled between 250~600 ℃, and the time is controlled between 12~48h.After the furnace temperature cooling, take out ball milling, finally obtain the iron phosphate lithium positive pole composite material of larger particles.
Comparative Examples
With Li: Fe: P=1: 1: 1 mol ratio ratio takes by weighing LiOHH
2O, FeC
2O
4And NH
4H
2PO
4, place ball grinder with 400~600 commentaries on classics/min speed ball milling 6h, after finishing mixture sent in the box type furnace and with about 350 ℃, handle 6h.Pretreated sample is carried out sending into behind the ball milling in the sintering furnace of nitrogen protection with 700 ℃ of roasting 24h again, take out the ball milling screening with the furnace temperature cooling and obtain lithium iron phosphate positive material.
Battery is made and performance test
The positive pole that is used for electric performance test is made up of according to 80: 15: 5 (mass ratio) the foregoing description and synthetic sample, SP and the polyvinylidene fluoride (PVDF) of Comparative Examples, after it is mixed with machine,massing, slurry on small-sized tensile pulp machine, using aluminium foil is 16 μ m, and the slurry surface density is 8~9mg/cm
2, as to electrode, electrolyte adopts conventional lithium battery electrolytes, is assembled into half-cell and tests with metal Li.Battery pack is contained in the glove box that is full of argon shield carries out H
2O and O
2All less than 1ppm.Carry out the constant current charge and discharge with 0.1C, charging is by voltage 3.8V, and discharge is by voltage 2.0V.
The finished product battery that is used for electric performance test uses technology to carry out according to the lithium battery production of routine.
To the The performance test results of the foregoing description and Comparative Examples gained positive electrode and made battery thereof as shown in drawings, 4000 times of sem photographs of Comparative Examples products obtained therefrom, XRD figure spectrum are seen Fig. 1, Fig. 3 respectively; 4000 times of surface sweeping Electronic Speculum figure of embodiment 1 products obtained therefrom, XRD figure spectrum are seen Fig. 2, Fig. 5 respectively; Semi-finished product XRD figure spectrum when also not carrying out secondary granulation behind the 4th ball milling among the embodiment 1 is seen Fig. 4; Fig. 6, shown in Figure 7 be to be respectively the discharge curve of battery under different discharge-rate conditions that adopts the positive electrode of Comparative Examples and embodiment 2 gained to make.
Carried out through the present invention as can be known by Fig. 1 and 2 that the particle of LiFePO4 sample obviously is the reunion shape behind the secondary granulation, average particle size distribution is obviously original big.
From not changing the crystalline form of lithium iron phosphate positive material after Fig. 3,4 contrasts lithium iron phosphate positive material and nickle cobalt lithium manganate ternary material mixing and ball milling as can be seen, the dephasign peak at place such as 2 θ=20 ° belongs to ternary material in the X-ray diffractogram of Fig. 4, thereby sample is the mixture of lithium iron phosphate positive material and ternary material; From Fig. 4,5 contrasts still is two kinds of mixtures of material through sample after 700~900 ℃ of calcinings as can be seen, is just becoming more sharp-pointed through high-temperature calcination rear portion swarming.
Each embodiment and Comparative Examples gained positive electrode are made the discharge scenario of the different multiplying of battery and are added up as shown in table 1:
The discharge scenario statistics of each embodiment of table 1 and Comparative Examples different multiplying
Sample |
1C discharge capacity/2C discharge capacity |
1C discharge capacity/5C discharge capacity |
Comparative Examples |
95.95% |
94.55% |
Embodiment 1 |
95.74% |
94.50% |
Embodiment 2 |
95.64% |
93.45% |
Embodiment 3 |
95.5% |
92.4% |
Embodiment 4 |
96.5% |
93.78% |
Embodiment 5 |
95.89% |
93.5% |
Embodiment 6 |
95.5% |
93% |
Embodiment 7 |
95.4% |
92.5% |
Embodiment 8 |
96.23% |
92.9% |
Embodiment 9 |
96.1% |
93.98% |
From Fig. 6 and 7 relatively, and table 1 is as can be known through after the present invention carries out secondary granulation, its multiplying power discharging property compare with the Comparative Examples of small particle diameter obviously do not reduce or even situation about increasing under, resulting sample not only particle diameter obviously increases, improved the tap density (as following table 2) of material greatly, processing characteristics strengthens.
The tap density test result of table 2 Comparative Examples and each embodiment sample
Sample |
Tap density g/cm
3 |
Comparative Examples embodiment 1 embodiment 2 embodiment 3 embodiment 4 embodiment 5 embodiment 6 embodiment 7 embodiment 8 embodiment 9 |
0.9~1.1 1.69 1.72 1.60 1.75 1.67 1.72 1.65 1..73 1.70 |
Pass through secondary granulation process of the present invention as shown in Table 2, the tap density of lithium iron phosphate positive material obviously increases, and has improved the volume and capacity ratio of material greatly.
The above embodiment has only expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.